This invention relates generally to car door operators for mass transit vehicles, more particularly concerning operators mounted overhead of a door opening in the vehicular side wall. The invention disclosed herein further relates particularly to power door operators incorporating helical drive/nut components and incorporating independent primary and secondary panel locks through prevention of drive member rotation and direct prevention of panel motion.
Overhead door operators incorporating helical drive members are well known in the field of mass transit door equipment. U. S. Pat. Nos. 3,745,705; 4,198,786; and 5,341,598 disclose overhead operators. All of the above mentioned operators utilize exposed helical door drive and exposed, axially displaced door hangers. In these arrangements there is a substantial force couple generated by offsetting the door drive and door hanger, thereby increasing wear on both the drive nut, hanger and any associated door panel lower guides. In addition, the physical displacement between the drive member and door hanger results in critical limited adjustment of the door panel with regard to motion transverse to the panel plane and hanger axis. Further, the exposed hanger and helical drive/nut combinations are particularly susceptible to contamination present in the application, including wear and dirt particles. Atmospheric corrosion is also a substantial problem.
The invention disclosed herein largely overcomes the difficulties through the use of a coaxial design wherein the helical drive member is disposed internal of and coaxial with a semi-cylindrical door hanger. This arrangement minimizes the force couple generated by the drive member- door panel spacing or offset. In addition, the door hanger utilizes upper and lower plastic rollers operating on the corresponding surfaces of the semi-cylindrical hanger. This arrangement greatly reduces the criticality of transverse door adjustment.
Also, a part of the invention disclosed herein is a greatly simplified door panel lock incorporating a ratchet cam and lock pawl combination which provides unidirectional rotation of the helical member. This allows precision positioning of the panel and prevents back driving the door panel through reverse rotation of the helix. The locking arrangement further includes a projection of the lock pawl through a slot or aperture in the door hanger whereby door panel opening motion due to a failure in engagement of the lock pawl and ratchet cam will be prevented by the continuing presence of the lock pawl in the aforementioned hanger slot. The design, therefore, provides truly independent primary and secondary door panel locks.
Therefore, it is an object of the invention to provide an overhead power door drive having inherent primary and secondary door panel locks.
It is an additional object of the invention to provide a power door drive having coaxial hanger and drive members minimizing door drive/door panel offsets and attendant wear producing forces.
It is a further object of the invention to provide a power overhead door drive wherein the helical drive member is completely contained within a semi-cylindrical hanger, thereby minimizing environmental and atmospheric contamination of the helical drive/nut engagement.
It is a further object of the invention to provide an overhead door drive wherein the coaxial relationship between a helical drive member internal of a semi-cylindrical door hanger utilizing cylindrically concave rollers intermediate the door panel and hanger surface provides simplified adjustment of the driven door panel.